The present invention relates to a surgical device for anchoring to the mucous membrane of the inner wall of the intestine, the device comprising an anchor element having at least one first semi-rigid hollow longitudinal element defining a wall forming a surface of revolution about a longitudinal axis with a substantially cylindrical multiply-perforated main portion of substantially circular section referred to as the “first” wall, said anchor element being made of a material giving it radial elasticity properties such that it can be compressed radially into a retracted position and can adopt a said maximally radially expanded position after the radial compression has been released, whereby said first multiply-perforated wall presents a diameter that can be varied in controlled manner.
More particularly, the present invention relates to an anchor device presenting anchoring that can be modified in controlled manner.
Elements for anchoring in the intestine are known, in particular devices known as “enteral prostheses” or “digestive stents”, which devices present a said first wall formed still more particularly as a mesh of spiral-wound wires, preferably made of nitinol, presenting properties of controlled diameter variation depending on temperature as described below, with an outer diameter that can be varied in controlled manner between:                a minimum first outer diameter in said radially retracted position of said first wall, preferably of at most 10 millimeters (mm); and        a maximum first outer diameter in said maximally radially expanded position of said first wall, preferably lying in the range 18 mm to 45 mm.        
Still more particularly, the present invention relates to a surgical device suitable for providing temporary protection for an anastomosis in the esophagus, the stomach, the jejunum, the colon, the rectum, or the anal canal.
In WO 2010/092291, and also in other documents such as WO 03/094785 and US 2008/0208357, said anchor element is coupled to an outer flexible sheath that extends in the same longitudinal direction as said stent, on the outside of said stent.
Those devices may be implanted 1) in the small intestine as described in WO 03/094785; 2) in the esophagus as described in US 2008/0208357 to combat obesity; and 3) in the colon, as described in WO 2010/092291 for protecting an anastomosis.
In other applications, in particular to avoid proliferation of cancer, a said stent is used without a said sheath solely for the purposes of providing permanent protection of the zone that is covered by said stent.
In any event, said anchor element must remain anchored in temporary or permanent manner against the wall of the intestine with said sheath extending downstream from said stent. In all of the applications mentioned above, it can happen that said temporary or permanent anchor elements separate from the wall of the intestine and migrate too soon.
In particular in the application of providing temporary protection for an anastomosis as described in WO 2010/092291, provision is made for the temporary anchorage to begin migrating after the end of the post-operative ileus period, which is estimated on average to be three days to five days. As a result, and because said outer sheath presents a length covering the distance between the anastomosis and the anchor site that is at least 50 centimeters (cm) upstream, and that is preferably at least 1 meter (m) upstream, said anchor is thus anchored far enough upstream from the anastomosis to ensure that when the digestive process restarts, the time it takes to migrate from said anchor position to said anastomosis is at least three days, and preferably at least six days.
Thus, insofar as the stage of post-operative intestinal paralysis, known as “ileus”, lasts for three to five days, it is possible to protect the anastomosis for that same period plus the time taken, after said anchor element has been released, for it to migrate from its anchor site upstream from the anastomosis to the site of the anastomosis, it being understood that this migration time depends on the distance to be traveled between the anchor site and the anastomosis. In practice, a distance of 50 cm to 1 m gives rise to a migration time of three days to six days, such that, in all, the anastomosis is protected for a duration of at least six days and possibly up to 11 days after making the anastomosis.
Nevertheless, it can happen that the post-operative ileus period is exceptionally short or on the contrary exceptionally long, with periods lying in the range 24 hours to four weeks, such that either the device migrates through the anastomosis before it has had time to heal, or on the contrary the device remains anchored in the intestine for too long.
In order to comply with an appropriate period for remaining within the intestine, it is therefore necessary to take account of the movements specific to the intestine of the operated patient. The greater the activity of the intestine, the faster the migration of the device, it also being understood that it is highly recommended to encourage post-operative intestinal activity in order to improve rapid rehabilitation of the patient.
For curative treatment of anastomotic fistulas after bypass surgery for morbid obesity, US patent No. 2008/0208357 describes a device for protecting the gastro-jejunal anastomosis. According to that patent, a protective sheath is secured to the downstream end of a stent. The stent is positioned in the bottom end of the esophagus where it is to remain in place as a result solely of its own characteristics. The protective sheath passes through the anastomosis and lies in the jejunum. The major drawback of that device consists in the risk of the stent migrating at an unwanted moment, and thus the risk of the entire device migrating into the intestine with at best the need to extract the device by endoscopic maneuvers, and at worse the risk of the intestine becoming occluded or perforated and making further surgery necessary. The risk of esophagus stents migrating remains significant, being about 20% for all stents.
Furthermore, the device described in the prior art for temporary anchorage and for protecting an anastomosis cannot prevent anastomotic fistulas arising, which fistulas take considerably longer to heal than the time the device remains in the intestine, in other words the temporary protection device runs the risk of being eliminated long before healing of a fistula, if there is one. Under such circumstances, the practitioner needs to make a protective stomy, which greatly decreases the therapeutic advantage of the device. From the above, it can be seen that the behavior of a device for providing an anastomosis with temporary protection, or more generally of a device for providing anchoring in the intestine, depends on factors that vary sufficiently between individuals to give it a random character, with the practitioner having no means for modifying the behavior of said anchor element once it has been implanted.
The time the device spends in the intestine depends on many factors such as the characteristics of the stent (radial opening force, resistance to compression, adaptability to deformations of the intestine, shape of the mesh, covering of its surface, etc.), the passive physical properties of the walls of the intestine (viscoelasticity), its dynamic properties (contractility), and also on the consistency of the stools. One of the factors that governs the behavior of the device is the force of friction that exists between the walls of the stent and the intestine. The greater the friction force, the slower the movement of the stent. Unfortunately, the coefficient of friction of the inner walls of the intestine is very low because of the presence of water, thus having the consequence of making it easier for the stent to slide.
This may be compensated in several ways. One consists in increasing the coefficient of friction of the outer walls of the stent by means of a covering film having adhesive properties. It has been shown that a textured surface, in particular when covered with micro-fibrils can present properties of greater adhesion (S. Buhl et al., Humidity influence on the adhesion of biomimetic fibrillar surfaces, International Journal of Materials Research, 2009; 100, No. 8: pp. 1119-1126). Nevertheless, that does not make it possible to exert direct control at will in variable amounts on the device in order to modify its behavior. Another method consists in increasing the diameter of the stent. However, apart from the risk of causing traumatic lesions in the walls of the intestine, that method likewise provides no direct control over the behavior of the stent. Finally, it is possible to use semi-resorbable hybrid stents in which the radial force decreases progressively as they are resorbed (Y. Shomura, Composite material stent comprising metallic wire and polylactic acid fibers, and its mechanical strength and retrievability, Acta Radiol. 2009 May; 50(4): 355-9). However, once more, the resorption process is not governed by any external action on the intestine, so it does not make it possible to exercise any direct control at will and in varying amounts on the device in order to modify its anchoring properties.
In other indications, digestive stents are used for remedying digestive stenoses. These may be stenoses of the esophagus, in particular those complicated by tracheal-esophageal fistula, gastric and duodenal stenoses, colonic and rectal stenoses. Some such stenoses can be treated by bare stents that serve to reduce the risk of migration at the expense of becoming incrusted in the wall of the intestine. Others are treated by stents covered in a film that serves to reduce the risk of becoming incrusted at the expense of increasing the risk of migrating.
It is thus still sought to provide a device that makes it possible to avoid the stent becoming incrusted in the walls of the intestine, while making it possible to control the risk of untimely migration.